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Arky, perhaps this is one of those issues that would get resolved with time. The spacing only has to be 135mm at the dropouts. There's nothing that says the chainstays can't stay fairly close near the BB then flair out past where heal clearance issues are a factor. However, this starts messing with the beautiful aesthetics that make a road bike so beautiful. I suppose we could all just start putting skinny tires on mountain bikes and forget about producing road bikes altogether, but wouldn't that be a shame.

What is the chainstay length on your CX bike and what size chainrings do you use?

I used a 135mm spaced bike (with BB7 rear brake) this fall, and with 425mm chainstays and 44/39 chainrings it was fine. Not sure it would be such happy days with 405mm chainstays and 50/34 rings.

All told, I think there's no way we aren't headed to 135, one way or the other. 11 speed Shimano, regardless of discs, makes 135 really attractive from the wheel's perspective.

Dave

Not sure of the chainstay length, but I'm running 46/38 rings. The stays are longer than a road bike would be though. I'm of the opinion that road bikes don't have to be 40.5cm in order to handle well.

All three of my current bikes have 135mm rear spacing. One has discs, one has canti's, and the other uses v-brakes. I also run the same cranks/pedals/saddles on all three bikes (so nothing feels "weird" when I switch). I pedal "toes out," and my heels strike the cranks before they clip the frame(s).

All three of my current bikes have 135mm rear spacing. One has discs, one has canti's, and the other uses v-brakes. I also run the same cranks/pedals/saddles on all three bikes (so nothing feels "weird" when I switch). I pedal "toes out," and my heels strike the cranks before they clip the frame(s).

Yes. 135mm is going to be the universal standard. Imagine being able to swap between road and mtn bike wheels on the same bike!

Keep in mind that 135 spacing came about and works well - but with compromises - for 3 chainring mountain bikes. So now when you have a dual chainring up front the optimal chainline (front vs rear) is not present......then say you run a std dual chainring you can have many more people having issues with heel strike occuring on the chain stays (if 135 in the rear).

If you use a 135, this puts the cassette 2.5 mm farther to the right (would be silly to do it otherwise). This means your chainrings must be located 2.5 mm farther right also, if you want to keep them centered. If the crank does not otherwise change, then both crank arms will be 2.5mm farther out... and you'd have slightly *less* tendency to hit your heel on the frame. But of course the cranks could be designed with the same stance as before... in which case you would. The heel already comes very close to the rear axle, so you can't gain anything by flaring out the chainstay. But it is a non issue for anyone who isn't very close to hitting the chainstay now.

There is one pretty big benefit to 135... you can increase the rear wheel DS offset ~14%... which makes the wheel stronger/lighter. Of course the manufacturers will quickly stick another gear in there, negating the benefit...

I pedal "toes out," and my heels strike the cranks before they clip the frame(s).

(MileHigh, the only part directed toward you below is my own experience with hitting cranks, the rest is toward the guys who influence the industry)

With a BB30 crank, you have the fortune of a narrower stance because your pedal arm can move in toward the narrower spindle. On my CAAD10, I hit the chain stay before my crank. I also experienced good crank clearance on the BB30 Kuota Kult. My stance will have to move out when chain stay moves out. Most manufacturers will not do a drastic S-bend (see the Franco bikes for example). The S-bend presents a slight loss in stiffness when the rear wheel lurches forward, compression loading the tube (unless weight is added to increase stiffness back to the same level). I used to have a signature quoting something like "we don't just need change, but change for the better". This is a great example of why this quote exists.

I like how the threshold has changed. When discs for cross first came out, I pointed out that it is inevitable for road, needed or not. When I predicted the spacing will change, the response was that we can fit in a little disc as is. The momentum is moving toward making my prediction right and we now will have to move the spacing to mountain bike width. We are supposed to accept it because the chain stays might bend outward at the dropouts? When that does not come into fruition, what then?

On a mountain bike you are not stationary in one position for hours on end. You move around out of necessity. On a road bike the change of stance will be noticeable. This is something that we should voice concerns about NOW while manufacturers are having high level discussions. The product managers need to figure out how to do a little disc or only do a disc in the front. Get together the product engineers, professional fitters, and frame builders and be prepared for a reality check about wider spacing. Do not become disillusioned by a pie in the sky obsolescence. Do not change just to hop on what you perceive to be the industry band wagon. Grow some balls, voice your opinion and think for yourself. Do what is best for the rider.

Arky, reality check? Seriously? I'm sure people with extreme toe-out stance that absolutely can't tolerate wider Q-factor at the same time are such a minority that it will be quite a surprise if manufacturers drop this move to 135 mm because of you. Sorry, man, but I don't see it happening.

Keep in mind that 135 spacing came about and works well - but with compromises - for 3 chainring mountain bikes. So now when you have a dual chainring up front the optimal chainline (front vs rear) is not present......then say you run a std dual chainring you can have many more people having issues with heel strike occuring on the chain stays (if 135 in the rear).

If you use a 135, this puts the cassette 2.5 mm farther to the right (would be silly to do it otherwise). This means your chainrings must be located 2.5 mm farther right also, if you want to keep them centered. If the crank does not otherwise change, then both crank arms will be 2.5mm farther out... .

It affectivly only puts one cog 2.5mm further out (smallest one) no need to move the chainrings out for that as you spend little time in the 11 anyway.

Ive got a road bike with disc and 135mm spacing, running a 12/27 and a compact on it and everything works fine

If you don't like 135mm, you can always buy up some cheap 130mm carbon frames, which I expect will be available on the 'For Sale' pages here in a year or two. Still, it's 'progress' like that which keeps the bike industry ticking along.

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